This invention relates to diazonium salts and a diazo-type material containing these salts for information-recording by means of light.
The operating principle of diazo printing involves producing a positive image on layers of solid binding agents provided on a polymer base by decomposing a diazonium salt through the action of light and, subsequently, reacting the unconnected diazonium salt with a coupler also provided in the layer of binding agents through the action of alkali agents, forming an azo dyestuff.
Previously, 4-dialkylaminobenzene-diazonium salts have been preferably used as light-sensitive diazonium compounds which may, in addition, comprise additional substances. Such compounds have absorption maxima between 380-410 nm (DE-OS Nos. 2 024 243, 1 693 195). It is possible to obtain an absorption maximum of 471 nm in the case of 5-methoxy-4-morpholino-2-nitrobenzenediazonium tetra fluoroborate (DE-OS No. 1 202 251). A more extensive bathochromy cannot be achieved with benzene diazonium salts.
The utilization of this kind of diazonium salt requires the use of energy-intensive, high-pressure mercury-vapor lamps, while the light emitted by them can only be partly utilized.
Light sources which radiate light in longer wave lengths, such as tungsten or halogen lamps, are not appropriate for the illumination of diazo-type materials that contain benzene diazonium salts.
Diazonium salts with absorption maxima around 560 nm have also been proposed (DD-WP G 03 c/213 282), which are sensitive to wave lengths from 540 to 600 nm. Even when these substances are used, only part of the lamp emissions can be used in photolysis.
It is the purpose of this invention to take advantage of the longer wave range of the lamp emissions and to expand the absorption range of the present diazonium salts.